Presently, 3GPP discusses a next generation mobile communication system as 3GPP-LTE (Long Term Evolution). According to 3GPP-LTE, a CN (Core network) and a UTRAN (UMTS Terrestrial Radio Access Network) are connected by an IP network. In data transport, a tunnel is established between the CN and the UTRAN. User data in the IP network is identified by identification information of the tunnel. This allows, for instance, transport of the data from the CN to an appropriate terminal (UE).
A TEID (Tunnel Endpoint Identifier) is typically used as identification information of the tunnel. The TEID is assigned when setting the tunnel. Assignation of the TEIDs is executed in the CN and the UTRAN. The TEIDs are exchanged between the CN and the UTRAN when respective RABs (Radio Access Bearer) are established. The TEIDs used for down link transport are assigned by the UTRAN and notified to the CN, and the TEIDs used for up link transport are assigned by the CN and notified to the UTRAN.
GTP (GPRS Tunnel Protocol) is used for actual data transport. A header of GTP-U, or U-Plane (User Plane) in GTP, is added to a packet (data packet) for transporting actual data. FIG. 1 is a diagram showing an exemplary configuration of the GTP-U header. Referring to FIG. 1, four octets of TEID are assigned to the GTP-U header.
The transmitting side apparatus transmits a data packet having the TEID assigned to the GTP-U header. The receiving side apparatus identifies the user data based on the TEID in the received data packet. For instance, with respect to down link data, the CN transmits a data packet having the TEID assigned to the GTP-U header. The UTRAN identifies the user (UE) with reference to the TEID assigned to the GTP-U header in the received data packet, and maps the data to a radio channel corresponding to the UE.
In 3GPP-LTE, an MBMS (Multimedia Broadcast/Multicast Service) that multicasts the same data to UEs is provided (see “Japanese Patent Laid-Open No. 2004-135260”, “3GPP TS25.413 V7.4.0 (2006-12), ‘UTRAN Iu interface RANAP signaling (Release 7)’”, and “3GPP TS25.414 V7.1.0 (2006-09), ‘UTRAN Iu interface data transport & transport signaling’”). According to the MBMS, in contrast to typical data communication, data is transported only in the down link. As described above, the TEID in the down link is assigned by the UTRAN and notified to the CN. Thus, according to the MBMS, the TEID is assigned only in the UTRAN, but is not done in the CN. The CN only transmits the data using the notified TEID.